We propose to study the joining of different DNA sequences - a phenomenon that we wish to call genetic fusion in Escherichia coli K12. This phenomenon is concerned with the formation of F- and R-prime factor plasmids, of transducing phages, and of mutations such as deletions, duplications, and translocations. These studies are intended to provide new understanding of the general characteristics of genetic fusion, which is distinct from general recombination, by identifying some of the special characteristics of the DNA sequences involved. These studies will be carried out by genetic methods, by electron microscope heteroduplex mapping methods and by using enzymes, such as restriction endonucleases, S1, exo III, etc., on DNA molecules of F- and R-primes, of their mutant derivatives, and of transducing phages. BIBLIOGRAPHIC REFERENCES: "Electron Microscope Heteroduplex Studies of Sequence Relations Among Plasmids of Escherichia coli: Structure of F13 and Related F-primes". Hu, S., Ohtsubo, E., and Davidson, N. (1975) J. Bacteriol. 122, 749-763. "Electron Microscope Heteroduplex Studies of Sequence Relations Among Bacterial Plasmids: Identification and Mapping of the Insertion Sequences IS1 and IS2 in F and R Plasmids". Hu, S., Ohtsubo, E., and Davidson, N. and Saedler, H. (1975) J. Bacteriol. 122, 764-775.